FIELD OF THE INVENTION
The present invention relates to a process of cold plastic deformation of metals in which special compositions are applied to the surface of a metal object such as a plate or sheet prior to mechanical forming or working (such as rolling, stamping or pressing). It relates therefore to agents that assist in the plastic working of metals, broadly referred to herein as plastic working agents for metals. The term "cold plastic deformation" is used herein to refer to the working of metals that have not been subjected to a heat preparation step.
Coatings have been applied to the surface of metal objects such as plates or sheets, particularly those made of steel to prevent impairment of the surface caused by friction between the surface and the shaping means, e.g. rollers or dies, and to protect the metal object from excess local temperature elevations, e.g., hot spots, or burning. Moreover, a hydrocarbon oil coating, often the same as or similar to the above coating is applied after forming or working to prevent rusting or oxidation of the surfaces during storage or transportation. The thus coated rolled sheet or plate is received at the site of further forming such as stamping or pressing, and here a liquid hydrocarbon lubricating oil coating is used in the further forming of the object into a desired shape for the purposes of reducing friction, preventing seizure or burning, preventing press streaks and reducing abrasion of the mold or die. It is believed by many technicians to be desirable to remove the rust-preventive oil before applying the liquid hydrocarbon lubricating oil coating, and this is commonly practiced.
Petroleum lubricating oils which have been used as the working coatings for the purposes described above have relatively and notoriously poor oil film strength, and therefore efforts have been made in the past to improve the oil film strength by adding to the petroleum oil an oil-soluble substance having a polar radical such as a fatty acid, a higher alcohol or an ester. However, even when such an additive has been incorporated, the liquid hydrocarbon lubricating oils which constitute the main component of prior plastic working agents retain or acquire undesirable characteristics; for example, steel plates so coated adhere closely together, dust sticks tightly to the surfaces and the oils of coatings flow during storage making it difficult to maintain a suitable oil film thickness.
On the other hand natural waxes of animal or vegetable origin such as beeswax or montan wax have fewer disadvantages than those possessed by liquid hydrocarbon lubricating oils, i.e. they are solid at ordinary storage and handling temperatures and they contain a high amount of esters. However, such natural waxes are expensive and their physical and chemical properties vary widely, because they are natural products. As a consequence, even the expensive natural waxes are not generally adaptable for the above described uses.